Process for producing seamless tubes



Jlme 1936- M. ROECKNER El AL 2,042,552

June 2, 1936. M. ROECKNER gr m. 2y042,552

PROCESS FOR PRODUCING SEAMLESS TUBES:

Filed Nov. 9, 1934 3 Sheets-Sheet 2 June 2,1936. M, R CKNER H 2,042,552

PROCESS FOR. PRODUCING SEAMLESS TUBES part of the billet which isreduced by the cutting Patented June 2, 1936 z,o42,5s2 rnocsss sonPRODUNG smmss TUBES Martin Roeckner and Joue Seirin, Mulheim- Ruhr,Gernmany, assignors to Deutsche Rohrehwerke AktiengeseflschaflaDugseldort, Germany Application November 9, 1934, Serial No. 752,282

' In Germany November 27, 1933 M (01. 80-62) part reduced by the firstpair of rolls is hih and? 5 Claims.

It is known to produce tubes irom a hollow billet by means of severalpairs of rolls arranged around-the billet a certain distance irom itsaxis, one roll of each pair acting on the wall from the inside and theother on the wall from the outside. In this known construction the rollshave dififerent widths or profiles; thus, the flrst pair of rolls cuts agroove into the billet, the groove being widened by the successive pairsof rollers, so that a=part 0! the billet reduced by the first pair ofrolls is graduafly stretched in the direction of one end of the hollowbillet. The inside and outside rolls 01 the pairs of rollers are in theknown construction so provlded that they roll on the outer and innerfaces of the billet on single track helical lines. The greater the pitchof the helical lines selected, the larger is that of the shoulders onthe first pair of rolls and which must be stretched towards the end in asingle rotation 01' the hollow billet, by the next pair of rollers. Thepitch must be such that the pairs of rolls can, according to theirwidth, stretch the reduced part of the billet in asingle rotation. Thegreater the pitch of the helical limes, the greater becomes the forcewhich is required in efiecting the change 01. shape. Furthermore, thedepth of the impression made by the sho1flders of the pairs 01 rollsmust be such that the part of the billet reduced by the flrst' that thewidth of a roll, which has been designed for use with a particularnumber of pairs of rolls for a particular thiclmess of wall of thehollow billet and a particular depth of groove,must be used with oneparticular pitch only. -If one of these dimensions should be chai1ged,it would theoreticafly be necessary for some other form of roll to beselectedotherwise there is the posis shaped to produce the finished tubeis dependent upon the pitch of the helicaHine track made upon theworking rolls and also by the depth of the groove. As the pitch ispossible 01 variation only wlthin relatively small limits, considerabledepths of groove are frequently selected in order to efiect thenecessary shaping more rapidly.

This means that, With a given source of power, the pitch of the tracksmade by the workingrolls must be small and the consequence is thatthe'narrow. The great disadvantage of this is that the metal 01 the billetat the reduced part does not move in the way that was intended towards.the neutral-plane of the wall of the tube that is. to be rolled, buttilts over sideways. The result is that the metal et the billet moves,under the pressure of the succeeding pairs of rolls, less and les in themanner intended and that at the position 0! change into the portions ofthe billet already rolled out a orease is formedat the base of thereduced part; this crease formed in the 4 passage of the billet betweenthe several pairs of rollers, gives' rise to excessive .rolling, whichis damaging to the finished article and affects its 15 In these figuresA is the wall of the hollow billet that is to be rolled, and B1, B2, B30 and B4 are the peflpheral portions of the working rolls.

these disadvantages. According to the invention The purpose of thepresent invention is to avoid the'shoulders of the first pair of rollsmake a 25 groove, which is not, however, as deep as is required but isquite shallow; 'it is then deepened by the succeeding pairs of rollsuntil the desired depth is reached.

Figures 5 to 8-illustrate how, with the same final depth of groove andthe same pitch, the

' metal at the reduced position moves smoothly, as

desired, towards the neutral plane of the Wall of the tube. According tothe invention the first pair of rolls B1 (Figure 5) makes a groove, but1ess 35 deep than required; the second pair of rolls then bath widensand deepens the groove towards the end. The third pair of rollscontinues both operations, and finally the fourth pair 01 rolls(Figure'8) ,stretches the metal to the final thick ness required for thewall.

The process of the invention not only affords protection aainst thetilting of a high narrow -ridge of metal that has been'produced by theflrst pair of rolls, but it also ensures uniform treatment right throughthe m'aterial by reason of the absolutely uniform movement of the metalduring the Whole working operation. For this reason the process Of' theinvention admits of the better utilization of the possibilities providedby an available source of power having a limited output. Thus, forexample, the pitch ofthe helical line styleof track for the workingrolls may be increasedwhile retaining the final depth of groove producedaccording to the prier proeess, or the depth of the groove niay beincreased pitch 01. the helica1 lines and. ro-

ducing the same depth of groove the rolling mil] is V means when therolls are disposed in, for example, two helical limes the pitch may bedoubled, so that the rolls penetrate only to hait the depth with thesame effort for each operation; By reason of the uniform change of formdue to the lesser depth of impression the speed of the rolling miil canbe increased, so that netwithstanding the lesser depth 01 impression andthe consequent increase in the requisite length et passage through therolling mil] for the material'being rolled. the total working time isreduced. Particularly advantageous is the disposition of the pairs ofrolls in a plurality of helical iines, if the shallow grooves pressed bythe flrst pair of rolls of the same heiical lines are increased to thedesired depth by the subsequent pairs ci rolls.

By operating in this manner with rolls disposed in multi-track helicallines a further disadvantage is avoided, which has made itseliobjectionable in connection with the known rolling method with rollsdisposed on a single track helical line. rolls, for example with fourpairs of rolls on a single trac]; -helical line, as shown in Figures 1to 8 of the accompanying drawings, the stretchmg 01 the work after itspassage through the pairs of rolls results in a wavy formation 01 theend face of the oncdming tube. If the plant be, for example, so selectedthat when there are; four pairs of rolls each pair affects one-quarterof. the total stretching, and if the billet be able to move ireelytowards the end then, il. the rolling operation is interrupted at anyparticule: mome nt, the distances betWeen the working portion o! eachroll and the rear end face 01. the

work measured on fines parallel to the axis of the tube, wouldnecessarfly difler,that is to say, the distance would, in the case ofthe fourth pair oi rolls be of necessity greater than in the case of thefirst pair 01! rolls by three-quarters of the total stretching. As,however, in the known processes the distance between the flrst and thefourth pair of rolls is only one-quarter of the periphery oif the tube,considerable forces must operate within this quarter of the periphery ofthe tube, striving to adjust themselves to the difl'erences in lengthreferred to. This is actuaily eflected in practice and involves theupsetting of the rolled-out part of the hollow billet, so

that the thickness of- Wall 01. the rolled tube when flnished is aiwaySgreater by several tenths than that which is calculated from the settingof the rolls.

This very important disadvaritage of the known mrocess as wellas thedanger et the over-tuming of the reduced part of the billet are avoidedor reduced to a practically negligible extent by the seiection ci.multi-track helicai lineS for the When working with several pairs of'working rolls. The considerable difference cf stretch before referredto, which exists, for example, in the case of four pairs of rolls withinone-quarter of the periphery of the tube, can be halved by selectingtwohelicai lines for the .5

- rolls instead of the one, without, however, there being any reductionin the total stretching, which stretching is .obtained by traversing thetwo-track helix the axial distance previosly covered in the On''trackheiix. The advantages of 10 having multi-track helical.lines for thesetting of the working rolls are made morefully evident as the number 01pairs of rolls increases. Figure 9 illustrates the diflerences ci.length which are theoretically produced at the advanc- 15 ing end faceof the work by four pairs of rolls disposed'on a single helical line.The letter A represents a development of the outside of the tube beingrolled. Figure 10 indicates the formation oithe advancing end face 01the work A where the pitch is the same for twotrack helical limes as forthe single helioal line, and the same stretch is obtained as in theexampie according to Figure 9.

Figures 11 to 14 show the meansaccording to 25 the invention iorobtaining the desired grooving or impression in a rolling mil] built forsix pairs of rolls, for increasing of the depth to which the singlepairs of rolls penetrates and further, the multi-track helical limes.tien there are provided two helical-lines each having three pairs ofrolls operating one behind the other. The disposition 01- the twohelical lines with respect to each other is shown in Figure 14, again inthe development of the work A, 35 and the influence of this dispositionupon the reduction in the diflerences or stretching in the advancing endface can be recognized.

The separate pairs'of rolls are so disposed on; their respective helicaipaths that the pairs 01. 40 rolls B1, B2, B3 and 31, B2, B3 are spacedat intervals o: V;th of the periphery of the work and each set of rollsis in close sequence. They may, however, be arranged in staggeredreiationship in such manner that the pair of rolls B1 is separated by ofthe periphery et the work being rolled irom the pair ci. rolls B1,naturally, however, only in such a way that the pair of rolls B1 remainson one line 01. the two helical lines selected and the pair 01 rolls Bi'remains on the otheriine. Similariy the pair B2 would be disposed behindthe pair B2, and B3 behind the pair 13:.

- We claim: r

1. A process for produczing tubes from hollow billets by stretchingprincipally in the axiai direction by means of a plurality of pairs ofrolls,

eonsistinginsubieeting the holiowbillet intended to form the tube torolling by pairs of rolls, the

inside and on the outside of the hollow billet, the axis of the saidrolls being out of alignment with the axis of the hollow billet and thesaid rolls being set to roll upon the outer and inner faces of thehollow billet in a helical direction, the rolls of the respective pairsof rolls being in succession et diierent and increasing width and ofdifferent and increasing depth et engagement, whereby a groove is formedin the metal of the hollow billet by the first pair of rolls and iswidened and deepened-succeasively by a, succeSsive flo'w of the metalproduced by each of the succeeding pairs of rolls so that the part ofthe billet reduced by the first pair of rolls is graduaily stretchedtowards one end et the hol- In this connec- 60 low billet without theformation of fissures or overtumings until the desired thickness of thework is attalned.

2. A process for produclng tubes from hollow billets according to qlaim1, wherein the groovlng of the hollowbflleb nd the widenlng anddeepening ofthe said roovlng are prod1xced by a plurality of pairs oirolls arranged one behind the other. v

3. A process for producing tubes from ho llow billets accordlng to lalm1, wheteln the groom lng of the hollow billet and the widening anddeepenlng of the said groovihg are produced b a plurality of pairsofrolls disposed upon a plurality of helieal fines.

4. A process for pmducing tubes frolm hollow billets accordlng to claim1, whereln the groovmg of the hollow billet and the widening anddeepenlng 01 the said groovlng are produced by a plurahty of pairs ofrolls arranged one behind the other and On a, plurality cf he1ica1limes.

5. A process for producing tubes from hollow billets accordlng to clalm1, wherein the groovlng of the hollow billet and the widening anddeepenlng of the sald grooving are produced by pairs of rolls arrangedOn a plurality of hlical llnes which deepen as far as required thegroove formedin the surfaces of the billet by the first pair of rolls onthe same helical fine.

MARTIN ROECKNER. JOSE smvmm.

